1. Field of the Invention
The present invention relates generally to the field of magnetic read/write heads and magnetic data storage, and more particularly, to a thin film write head, and method of making such head, including a separator layer of insulating material providing a cover over front and back tips of the top pole to reduce the separation distance between the bottom coil turns and the front and back pole tips which reduces the yoke length.
2. Relevant Background
Data is stored on magnetic media by writing on the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular area on the magnetic media. The state of the magnetic moment is later read, using a read head, to retrieve the stored information. Data density is determined by the amount of data stored on an area of magnetic media and depends on how much area must be allocated to each bit. Data on magnetic media is often stored in a line or track. Magnetic media often have multiple tracks. In the case of disks, the tracks are nested annular rings with more bits per track and more tracks per disk increasing data density. Data density or areal density, therefore, is determined by both the bit length and by the width of the bit. To decrease bit size, head size is decreased by fabricating thin film read and write heads.
Ongoing, important goals of researchers in magnetic recording technology include producing disk drive read heads that achieve strong signals, providing accurate read back of those signals, minimizing noise interference, and providing very high areal density while controlling manufacturing costs. Unfortunately, some of these goals directly conflict with one another. For example, to achieve ever-higher areal densities, track widths on a disk become smaller necessitating that the components used to read and write data also become smaller, which makes manufacturing more difficult and expensive.
Generally, the writer element of a thin film head is fabricated using top and bottom magnetic pole pieces and a multi-turn coil, which is wound between the top and bottom poles. The coil is defined on top of the lower pole prior to the formation of the upper pole. FIG. 1 illustrates one exemplary prior art read/write head fabricated as a conventional composite-type thin film magnetic head, and the following is a brief description of typically head manufacturing steps of such a head. The composite type thin film magnetic head in this embodiment has a reading GMR reproducing element on a substrate and a writing inductive type thin film magnetic head stacked on the reading element. Since in practically manufacturing a thin film magnetic head, many thin film magnetic heads are formed on a wafer at the same time, the end of each thin film magnetic head is not shown.
An insulating layer 2, e.g., alumina, is formed in a thickness of about 1 to 5 μm on a substrate 1, e.g., AlTiC, on which a first magnetic layer 3 constituting one magnetic shield layer to protect the reading GMR element from an external magnetic field is formed in a thickness of 2-3 μm. Then, a first shield gap layer 4 is sputter formed of an insulating material, e.g., alumina, in a thickness of about 50-150 nm, and thereafter a multilayered structure-magnetoresistive layer 5 constituting the GMR reproducing element is formed such as at a thickness of less than 100 nm. For forming the magnetoresistive layer 5 into a desired pattern, a photoresist layer is formed on the layer 5. The photoresist layer can be formed in a shape for easy lift off, for example, a T-shape. Next, the magnetoresistive layer 5 is ion-milled through the photoresist film as a mask, and thereby is formed in a desired pattern. Then, a second shield gap film 8, e.g., alumina, is formed in a thickness of 50-150 nm to embed the magnetoresistive layer 5 into the first and second shield gap layers 4, 8, and a second magnetic layer 9, e.g., permalloy, is formed in a thickness of 2-6 μm. The second magnetic layer 9 works not only to magnetically shield the GMR reproducing element along with the magnetic layer 3, but also as the bottom pole in the thin film recording head.
A write gap layer 10 made of nonmagnetic material, e.g., alumina, is formed in a thickness of about 50-300 nm on the second magnetic layer 9 and thereafter an insulating layer 11 made of photoresist is formed in a thickness of 0.5-2 μm corresponding to a given pattern. Then, a first layer, thin film coil 12 is formed, such as in a thickness of 3 μm, with a photoresist film 13 providing insulation separation from the top pole 16. The insulating layer 13 made of photoresist to cover the first layer-thin film coil 12 is typically flattened by a thermal treatment, and a second layer-thin film coil 14 is formed, such as in a thickness of 3 μm, so as to be insulation separated by and also supported by an insulating layer 15 made of photoresist. The insulating layer 15 made of photoresist to cover the second layer-thin film coil 14 is flattened by a thermal treatment, and thereafter, a third magnetic layer or top pole 16 is formed corresponding to a given pattern and is typically made of a permalloy material or FeN material having a high saturated magnetic flux density.
Fabrication of the head shown in FIG. 1 has presented a number of challenges and sometimes less than desirable results. The coil element 12 is insulated from the front and back (or adjacent) pieces of the top pole 16 by cured photoresist 13, and to achieve desired insulation results, the final dimensions of this photoresist insulation 13 must be carefully controlled to insure that it is thick enough to not only effectively insulate the coil turns 12 but to also endure subsequent manufacturing processes without erosion that would expose the coil 12 (i.e., fail to adequately insulate the bottom coil 12 from the top coil 14 or the top pole 16). As a result, prior art heads have generally been fabricated with a relatively large thickness of photoresist between the end turns of the bottom coil 12 and the adjacent front and back pieces of the top pole 16, as shown by the separation distance, dSEP, in FIG. 1. Additionally, the slope (as shown at 17) of the cured resist insulator 13 must be controlled within exacting limits to allow formation of the top pole 16 by photolithography. These two limitations result in extended processing times to properly cure the resist insulator 13. Further, the top pole 16 has an undesirably large yoke length, LYOKE, to accommodate the larger coil and insulator stacks. Head fabrication is further complicated because photolithography of the top pole 16 must be performed on surfaces with substantial topography and large step heights that can result in ineffective control of the dimensions of the elements of the produced head.
Hence, there remains a need for a thin film write head and corresponding manufacturing processes that support the need for tight dimension controls and adequate insulation between coils and pole elements while reducing fabrication complexity, processing times, and costs and furthering head design goals such as reduced pole length.